v0.2.1: building_eload split profiles, stable open-data bus ids

- Read energy_model_static/hourly_<district>.parquet from building_eload
  >= 0.6.0, with fallback to the legacy single file (#2).
- Open-data bus ids no longer depend on DuckDB scan order; they may differ
  from those produced by 0.2.0 (#3).